Bus system for an agricultural vehicle

ABSTRACT

The invention relates to a bus system comprising a bus line, to which electronic devices ( 26 - 36 ) can be connected. According to the invention, at least one electronic device ( 36 ) can be connected via a detachable interface ( 38 ) to the bus line, said interface ( 38 ) having a first connection ( 42 ) that is connected to a first section ( 12 ) of the bus line and a second connection ( 44 ) that is connected to a second section ( 14 ) of the bus line. To prevent an interruption of the bus line when the interface ( 38 ) is free, a bypass device ( 40 ) automatically creates a connection between the first section ( 12 ) of the bus line and the second section ( 14 ) of the bus line, if no electronic device ( 36 ) is connected to the interface ( 38 ).

[0001] The invention pertains to a bus system, with a bus line, to whichelectronic devices can be connected, wherein at least one electronicdevice can be connected to the bus line at a separable interface,wherein the interface contains a first and second terminal connection inthe motor vehicle, and wherein the first terminal connection isconnected to a first section of the bus line and the second terminalconnection is connected to a second section of the bus line.

[0002] DE 196 24 027 A describes an on-board computer system formachines which comprises a detachable on-board computer with memory,input devices and display devices.

[0003] EP 0 203 662 A describes a communication system for transmittingelectronic messages between an agricultural machine and a tractor,wherein said communication system contains a bus in the form of a line.Electronic controllers for controlled devices, display devices andsensors are respectively connected to the bus via assigned terminalunits. The bus transmits the data in serial form.

[0004] Today, bus systems of this type are usually realized in the formof so-called CAN.buses. They contain a continuous bus line, at both endsof which one respective matching resistor is arranged. All controllingand controlled controllers of the connected devices are connected to thebus line. The CAN specification allows only feeders with a length of 1 mbetween the backbone and the connected devices or controllers. Theagricultural interpretation according to ISO 11783 also prescribesfeeders with a length of only 1 m. This means that the bus line mustextend into the vicinity of the plug of the connected devices orcontrollers. Consequently, the bus line runs twice in many sections ofthe wiring, namely from the main cable harness to the device plug andback again.

[0005] In instances in which a detachable device should be connected tothe bus line, the above-mentioned standard stipulates the utilization ofa plug connector, wherein the bus line is cut in the vicinity of thedevice (e.g., underneath the cabin console) and expanded with a T-shapedwiring arrangement. In this T-shaped wiring arrangement, the bus lineextends from the backbone to a second plug connection, to which thedevice can be connected, via a first plug connection. The bus line thenextends from the second plug connection to a third plug connection whereit is connected to the backbone again. In order to observe thespecifications of the above-mentioned standard with respect to thelength of the feeders, the two sections of the bus line must extendthrough the second plug connection. The connection between the twosections of the bus line is formed by the cable that is connected to thedevice and must be connected to the plug connection (or in the device).When the device is disconnected, it is necessary to produce a connectionbetween the two sections of the bus line in order to prevent aninterruption of the bus line. A suitable plug is provided for thispurpose.

[0006] In this respect, it is disadvantageous that when connecting anddisconnecting the device, the bus line is interrupted during the time inwhich no plug is located in the plug connection. The bus line is notfunctional when the device is disconnected and no plug is provided forproducing the connection between the sections of the bus line.

[0007] The invention is based on the objective of making available animproved bus system in which the function of the bus line is alsoensured when the device is disconnected.

[0008] According to the invention, this objective is realized with thecharacteristics of claim 1, with the subordinate claims disclosingcharacteristics for realizing advantageous additional refinements of theinvention.

[0009] The invention pertains to a bus system of the initially describedtype. Two sections of the bus line extend through a separable interfacethat serves for connecting an electronic device in the form of anappliance, a switchbox, a terminal, a controller or the like in adetachable fashion. The two sections of the bus line are connected onthe side of the interface which faces the electronic device when anelectronic device is connected to the interface. In order to prevent thefirst section of the bus line from being separated from the secondsection of the bus line when no device is connected to the interface,the invention proposes a bypass device (in the motor vehicle) whichautomatically produces a connection between the first section and thesecond section of the bus line when the interface is not in use, i.e.,when no electronic device is connected to the interface. The bypassdevice is correspondingly controlled if the interface is not in use andconnects the two sections of the bus line to one another. If anelectronic device is connected to the interface, the bypass deviceautomatically separates the connection between the two sections of thebus line. It should be emphasized that the two connections of theinterface which are connected to one section of the bus line do not haveto be combined in one plug connection or the like. The interface mayalso contain two separate plugs or the like. The bypass device thenseparates the connection between the first section and the secondsection of the bus line if both plugs are connected to the interface.

[0010] Due to this measure, interruption of the bus line is preventedwhen no electronic device is connected to the interface. It is no longernecessary to arrange a plug on the interface for restoring the busconnection when the electronic device is disconnected.

[0011] The bypass device preferably contains an electronicallycontrolled switch that is designed for connecting the first section ofthe bus line to the second section of the bus line. The switch may berealized in the form of a relay or with other electronic switchingmeans, e.g., transistors or the like. This switch is controlled by theinterface for the electronic device. In this case, the status of theinterface can be determined mechanically, wherein a plug that isinserted into the interface mechanically opens or closes a contact inorder to control the switch. However, it would also be conceivable todetermine the status of the interface electronically, for example, bymeans of an inductive proximity switch. According to the invention, itis preferred to control the switch electronically via the interface. Acontact on the interface which is assigned to the switch is onlyconnected to a certain potential, for example, ground potential or theoperating voltage, when an electronic device is connected to theinterface. The switch then connects or separates the first section andthe second section of the bus line in accordance with the potential ofthe contact assigned to the switch.

[0012] The bypass device usually is arranged relatively close to theinterface so as to maintain the length of the free feeders to theinterface within the range defined by the above-mentioned standard. Ifthe bypass device is arranged farther from the interface, the bus linesbetween the bypass device and the interface can be automaticallyseparated from the remaining bus by the bypass device so as to preventundesirable interferences of the bus line.

[0013] The bus line transmits, in particular, electrical signals.However, it would also be conceivable to utilize an optical bus line.

[0014] One embodiment of the invention is described in greater detailbelow with reference to the figures. The figures show:

[0015]FIG. 1, a block diagram of a bus system, and

[0016]FIG. 2, a circuit diagram of a bypass device.

[0017]FIG. 1 shows a block diagram of a bus system according to theinvention. This bus system contains a bus line that is composed of afirst section 12 and a second section 14. The second section 14 of thebus line is connected to a third section 20 of the bus line via a plugconnection that is composed of a first connector 16 in the form of amatching resistor that switches off automatically and a second connector18. The bus line is terminated on its left end by a first matchingresistor 22 and on its right end by a second matching resistor 24. In anagricultural vehicle, the first section 12 and the second section 14 ofthe bus line may be arranged on a motor vehicle (e.g., a tractor) andthe third section 20 of the bus line may be arranged on an attached ortowed device (e.g., a sprayer). Electronic devices 26-36 are connectedto the bus line. The electronic devices 26-36 contain electroniccontrollers that communicate with one another in serial form via the busline. The electronic devices are assigned to controlling devices (e.g.,input devices), display devices (virtual terminal), controlled devices(e.g., spraying nozzles) or other electronic (control) devices. The busline may consist of a multi-wire bus line. Bus systems of this type aregenerally known and, for example, specified in standard ISO 11783.

[0018] An electronic device 36 is detachably connected to the bus systemvia an interface 38 in the form of a plug connection consisting of aplug and socket. The first section 12 and the second section 14 of thebus line are each connected to the interface 38 via a bypass device 40.The interface 38 contains a first connection 42 that is connected to thefirst section 12 of the bus line and a second connection 44 that isconnected to the second section of the bus line. The first section 12and the second section 14 of the bus line run to the electronic device36, where (or in the vicinity of which) they are connected to oneanother via the interface. This means that the bus line is connectedthrough the interface to the electronic device 36. If the electronicdevice 36 is disconnected from the interface 38 and no devices areconnected to the interface 38, the bus line is interrupted at thislocation. According to the state of the art, a corresponding plug mustbe arranged on the interface 38 for electrically connecting the firstsection 42 and the second section 44 to one another when the electronicdevice is disconnected.

[0019] The bypass device 40 is equipped with a switch 46 in the form ofa relay. If a voltage is applied to a line 48 that is connected to theinterface 38 as shown in FIG. 1, the switch 46 that is designed forconnecting the first section 12 and the second section 14 of the busline to one another is open. This means that the first section 12 andthe second section 14 are not connected to one another by the switch 46.The line 48 is supplied with an electric voltage (e.g. +12 V) by acontact of the interface 38 which is assigned to this line. If theinterface 38 is separated when the electronic device 36 is detached, avoltage is no longer applied to the line 48 and the switch 46 closes.This causes the first section 12 and the second section 14 of the busline to be automatically connected to one another such that the bus linealso operates flawlessly when the electronic device 36 is detached fromthe interface 38.

[0020]FIG. 2 shows an embodiment of the bypass device 40 for a CAN.bus.This bypass device contains an interface 38 in the form of a plug 38 b(for the user station according to the LBS standard), into which acoupler 38 a that is electrically connected to the electronic device 36can be inserted. The bypass device 40 is connected to the two sections12 and 14 of the (two-channel) bus line by plug connections, with saidbus line comprising two data channels (CAN H and CAN L) and two powersupply lines (TBC-PWR and TBC-RTW). In addition, the bypass device 40 isconnected to a power supply line (+12 VDC and GRD) installed in parallelwith the bus line via a plug connection, with said power supply line, aswell as the power supply channels of the bus line, being connectedthrough the bypass device 40. This means that the bypass device 40 canbe disconnected and removed from the bus line. However, it would also beconceivable to permanently connect the bypass device to the bus lineand/or the power supply line, as indicated in FIG. 1.

[0021] The plug 38 b of the interface 38 contains contacts, wherein onerespective contact is connected to the power supply lines and to thedata channels of the first section 12 and the second section 14 of thebus line. The line 48 for controlling the switch 46 that is realized inthe form of a relay is connected to a contact of the plug 38 b, withsaid contact being connected to +12 V via the corresponding contact ofthe coupler 38 a if the plug 38 b and the coupler 38 a are connected toone another. In this way, the contacts of the switch connect the datachannels of the first section of the bus line 12 to the data channels ofthe second section of the bus line 14 when the plug 38 b and the coupler38 a are not connected to one another as shown in FIG. 2. Otherwise, theswitch 46 is open and the bus line conventionally extends through theinterface 38. As with the data channels, the power supply lines of thebus line may also run through the interface 38 so that they can bechanged over.

1. Bus system, containing a bus line, to which electronic devices(26-36) can be connected, wherein at least one electronic device (36)can be connected to the bus line at a separable interface (38), whereinthe interface (38) contains a first connection (42) and a secondconnection (44) in the motor vehicle, and wherein the first connection(42) is connected to a first section (12) of the bus line and the secondconnection (44) is connected to a second section (14) of the bus line,characterized by the fact that a bypass device (40) automaticallyproduces a connection between the first section (12) of the bus line andthe second section (14) of the bus line if the interface (38) is not inuse.
 2. Bus system according to claim 1, characterized by the fact thatthe bypass device (40) does not produce a connection between the firstsection (12) and the second section (14) of the bus line if anelectronic device (36) is connected to the interface (38).
 3. Bus systemaccording to claim 1 or 2, characterized by the fact that the bypassdevice (40) contains an electronically controlled switch (46), inparticular, a relay, wherein said relay is designed for connecting thefirst section (12) and the second section (14) of the bus line, and bythe fact that the switch (46) is controlled by the interface (38). 4.Bus system according to claim 3, characterized by the fact that theswitch (46) is controlled by the interface (38) in an electrical,electromechanical or mechanical fashion.
 5. Bus system according to oneof claims 1-4, characterized by the fact that the bypass device (40) isarranged close to the interface (38).
 6. Bus system according to one ofclaims 1-5, characterized by a bus line that transmits electricalsignals.
 7. Bus system according to claim 6, characterized by the factthat the bus line consists of a CAN.bus.
 8. Bypass device (40) for a bussystem according to one of the previous claims.
 9. Utility vehicle oragricultural vehicle and/or device with a bus system according to one ofthe previous claims.